Current processing tools are requiring tighter dimensional tolerances for a number of components. An example of one type of component is an electrostatic chuck used for processing wafers in a plasma. An electrostatic chuck uses an electrostatic potential to secure the wafer to the chamber electrode during wafer processing. The alignment of components responsible for placing and processing the wafer within the processing chamber is highly critical, particularly when using an electrostatic chuck. During an etch or deposition process, slight misplacement of the wafer on the electrostatic chuck can result in nonuniform processing or other undesired effects. Additionally, the misalignment of the substrate on the electrostatic chuck can result in excessive leaking of a backside coolant gas and cause a fault condition to occur that prematurely terminates processing.
The prior art uses a variety of alignment schemes attempting to achieve the tight alignment tolerances required by electrostatic chucks. In one aligning scheme, a metal wafer with a hole in the center is placed onto a substrate handler. The metal wafer is then visually aligned to a gas port located within the electrostatic chuck. This alignment is subject to inaccuracies because it is a visual technique, and the results are highly variable.
In yet another embodiment, an aligning tool or jig can be used to perform the alignment. For example, the Applied Materials 5300 Centura.TM. platform, manufactured by Applied Materials, Inc. of Santa Clara, Calif., uses an alignment tool similar to the one shown in FIG. 1. The alignment tool 10 includes a ring 12 with a raised portion 14 having a hole 16 through the center. After the alignment tool is aligned to the electrostatic chuck (not shown), a substrate handler (not shown) is inserted into a portion of the alignment tool 10. A pin 20, as illustrated in FIG. 2, is inserted through hole 16 in the alignment tool 10 and through a hole in the substrate handler. Once the shaft 22 of the pin 20 falls through the hole in the substrate handler, the system is aligned. As shown in FIG. 2, the shaft of the pin 20 is of relatively constant width from the shoulder of the tool 24 downward.
Problems can be encountered with this alignment scheme. The alignment of the tool 10 to the chuck is performed by snugly placing the inner diameter of ring 12 along the outer diameter of the electrostatic chuck. Because the alignment is circumference to circumference, any deviation or machining tolerance variations along the diameter of either surface can be problematic. Since the alignment tool 10 is portable and is frequently moved, the ring 12 is susceptible to physical damage and deformation from being dropped or mishandled, or as a result of exposure to extreme temperatures.